"No, port supply source...depot on fleet lost" bug
This has happened twice in the same PBEM game. A GB one-factor HF had a depot onboard for invasion supply. The depot was suddenly removed and the event recorded (see language above) even though there are at least 2 unblockaded British supply-source ports with fleet counters and depots. The fleet with the depot was not moved in any way. In the files attached, this occurred immediately following the June British naval phase. Earlier it happened in the April Land/Land combat between the Prussian and French phases.
Annoying in that it requires GB to spend an additional $$ to place a new invasion supply depot.
I've seen this bug many times, too. As GB, it's not so bad, because it just costs $1 to rebuild it. But, it's money that shouldn't need to be spent.
I tried some playtesting with this, and I found that it ALWAYS deletes the depot on a fleet at sea. Furthermore, it does not do so until after naval movement is complete. I did not have any naval battles, so I couldn't tell if it was between naval move and naval combat. But, they were gone at the beginning of the land movement phase, yet present at the beginning of the naval move phase.
NOTE: The depot which was the supply source for these depots was never removed, no was at least one fleet that was in that port (which isn't even required, but I just wanted to rule that out).
I have got the same with the Turks.
I am invading Egypt and thought to use sea supply to save money. I was able to supply my troops cheaply off the coast but after I ended the land phase it has been deleted.
At least I got to it for the one turn I need it.